Microsoft is more willing to work with us. We have Microsoft services plastered all over our website. Yet we don't have a single app for their mobile platform. In case you guys didn't know, Facebook owns Instagram. So why with such willingness to work together is there no official Instagram, Facebook, Facebook messenger app? Why isn't Microsoft pushing??

Facebook are waiting for more financial "incentive" from MS ;-) They know MS really needs those apps for the WP platform and they know MS would be willing to pay them for development... Perhaps MS already offered them a certain amount but it wasn't large enough, so they are probably waiting for a better offer ;-)

This is a demonstration of how large companies have different priorities and different divisions have different incentives. Apparently there was enough incentive from Bing for Facebook to go with that over Google. I doubt MS would turn down a huge deal for their search platform unless Facebook builds an app for Windows Phone. While it is frustrating to see the isolation that occurs it is just part of normal business.

Microsoft is more willing to work with us. We have Microsoft services plastered all over our website. Yet we don't have a single app for their mobile platform. In case you guys didn't know, Facebook owns Instagram. So why with such willingness to work together is there no official Instagram, Facebook, Facebook messenger app? Why isn't Microsoft pushing??

And please, don't anybody talk about the 'built in integration'.

It's because you are thinking of Microsoft as a monolith organisation rather than (like most organisations) a series of computing fiefdoms - the team behind BING are tasked with making it the most successful search engine, that is their purpose. A tie-in with facebook is excellent for that team, it's not their job to care what is good for the WP team. The whole history of Microsoft is based on internal competition. In the past, many web features were killed off because they might impact the sales of MS office and the office team was more powerful than the web services teams.